Vinyl chloride and vinylidene chloride polymers are known to be self-extinguishing and relatively more flame retardant than other polymers such as polyethylene, polypropylene and the like. However, a substantial amount of smoke may be produced upon exposure of vinyl chloride and vinylidene chloride polymers to a flame. The fact that an additive is a flame retardant does not necessarily mean that it will have good smoke retardant properties.
Inorganic and organometallic complexes of molybdenum are commercially useful as smoke suppressants in halogenated resins. Various amine molybdates have been investigated by B. F. Goodrich, see U.S. Pat. No. 4,153,792, for smoke suppression in PVC compounds. These compounds were plagued with poor performance properties due to residual molybdenum trioxide. The residual MoO.sub.3 causes blue discoloration of the resin systems coupled with poor thermal stability.
The most commercially recognized material for smoke suppression in PVC is ammonium octamolybdate (AOM). AOM is the premium material to make low smoke PVC compounds, particularly for plenum wire and cable applications. AOM is used in numerous PVC jacket formulations that pass the rigorous UL910 test for cables (cooper conductor and fiber optic cables).
U.S. Pat. No. 4,153,792 discloses the production of amine molybdates, especially melamine molybdate by reacting an amine, such as melamine, with molybdenum trioxide in an aqueous acidic medium under reflux.
U.S. Pat. No. 4,217,292 discloses the production of amine molybdates, preferably melamine molybdate by reacting an amine such as melamine with a stoichiometric quantity of molybdenum trioxide in an aqueous medium in the presence of an ammonium salt. The aqueous medium is essentially free of acid. The reaction may be conducted at temperatures within the range of 75-110.degree. C.